They definitely existed, not as gun buggies with the RM but as towing tractors on HMS Bulwark and as lightweight pickups . Too late for Suez, no real use in Aden or Borneo, save for the ship-board tractor role and all three services went Land Rover crazy in the 1960s.
By the by the 'lightweight' option for RCLs in the mid 1950s through to early mid 1960s was the M40 106mm RCL, there are extant photos of them mounted by the paras on Austin Champs in Suez and elsewhere. I doubt that 75mm RCLs would have been specifically purchased for these.
A single item did see service in Algeria with the French Army and it's fairly well documented photographically. Both the 75mm RCL and a 20mm Mauser cannon (Empress and Eureka respectively in 28mm) were fitted.
https://2cv-legende.com/2cv-militaire-1961https://tanks-encyclopedia.com/2cv-ghan1/The modern rebuild seems to be an homage to that one.
Still, as a 'what if' it's a magnificent bit of kit. I note you already have a 2CV but there's a fabulous, wargamer simple 1/43 kit of the 2CV by Heller, if you fancy chopping one into these. I know you really want one as a justification to put your old Lloyd Cole records on the turntable.
